Plot

Plot

Weeks after the events that led to Lex Luthor's arrest, the impeachment of his presidency, and Superman and Batman's success in saving the world from a kryptonite meteor, a spaceship crash-lands in Gotham City Harbor. While Batman investigates the sunken craft, a young girl emerges from the water and accidentally wrecks Batman's boat. She is naked and has no knowledge of Earth languages or customs. On the shore, she encounters three longshoremen, one of whom tries to advance on her. She attacks two of them out of self-defense, while the third one gives her his coat to cover herself. As the girl progresses into the city, she inadvertently wreaks havoc with her strong Kryptonian powers (with Batman in pursuit) until Superman arrives to correct the damage, allowing Batman to eventually expose her to a piece of Kryptonite which weakens and injures her mentally.

With Superman's help, they discover the girl is Kara Zor-El, the niece of the late Jor-El and Lara, making her Superman's biological first cousin. She has been in suspended animation for decades due to her rocket crashing off course. This results in Kara being physically younger than her younger cousin. While Superman welcomes Kara, teaches her English, and helps her adjust to Earth's society, Batman remains suspicious even considering the possibility of Kara being an enemy. Kara states that she would never hurt her baby cousin. After which she tells Batman that he doesn’t have a heart. Tipped off by Batman, Wonder Woman and Lyla ambush Kara and Clark Kent, Superman's alter ego, in a park and suggest they train Kara at Themyscira, the only place where she can learn how to control her powers. Superman reluctantly agrees to let them train Kara, but still prefers to watch over her himself; however, Batman and Wonder Woman inform Superman to steer clear of Kara, criticizing him of his care for her.

On the desolate planet Apokolips, Darkseid learns of Kara's presence on Earth and orders Granny Goodness to have her brought to Apokolips as a possible leader for the Female Furies, as Big Barda is no longer his servant and the warrior Treasure being a failed candidate. Two months later, Batman and Superman are checking on Kara on Themyscira during a sparring match against Artemis. While Kara and Lyla later sneak away for a swim, a horde of Doomsday clones arrives from Apokolips. Superman, Wonder Woman and the Amazonian army fight them until Superman vaporizes them all with his heat vision. Batman, however, guesses the reason for the clones' attack and discovers Kara missing and Lyla dead; a last manifestation of her precognition reveals that the culprit is none other than Darkseid, who ordered a diversion to keep them busy allowing time for Granny to kidnap Kara. After being brought to Apokolips, Darkseid brainwashes her into serving him and she wears a seductive outfit and a sharp hairstyle.

To save Kara, Batman, Superman and Wonder Woman recruit Big Barda to help them find their way on Apokolips. There, Superman infiltrates Darkseid's palace while Wonder Woman and Barda go through the sewers directly into the fighting arena, where Granny Goodness and the Female Furies ambush them. After a hard fight, Granny and the Furies are subdued. Separating himself from the others, Batman finds Darkseid's supply of Hell Spores, the source of the fire pits on Apokolips. Superman encounters Darkseid, demanding that Kara is to go back with him. Darkseid says that Kara may leave, if she wants to, but sets Kara on Superman. Kara fights a reluctant Superman while Darkseid watches, until Batman confronts Darkseid and informs him that he has activated the Hell Spores, which will destroy Apokolips. He issues Darkseid an ultimatum: free Kara and promise to leave her alone, and Batman will deactivate the Spores. Superman defeats Kara, and Barda and Wonder Woman present Darkseid with the subdued Granny, whereupon Darkseid finally releases Kara, and the heroes leave Apokolips, bringing Kara back to Themyscira.

Back on Earth, with their lives apparently normal again, Clark takes Kara to meet his adoptive parents in Smallville. However, Darkseid, who was waiting to kill Superman, ambushes them: he had promised to leave Kara alone, but not Superman or Earth. Darkseid almost kills Superman with his Omega Beams before Kara takes the blast for her cousin. Superman attempts to fight Darkseid, but is quickly overwhelmed by Darkseid’s vastly superior prowess and punched into space. Kara engages Darkseid in a lengthy battle and manages to hold her own, having received Amazonian and Apokoliptan training, but he eventually gains the upper hand and knocks her into unconsciousness with a single kick. Before Darkseid can leave, Superman returns to Earth and reengages him. Superman sends Darkseid through the barn and attempts to crush him under a mountain. This fails to even scratch Darkseid as he severely injures Superman with a single blast of omega beams. Quickly Superman pummels the villain with all his strength. Superman only manages to give Darkseid a small nosebleed and Darkseid easily regains his hold and tortures Superman with his Omega Beams almost killing him. Kara recovers and uses Darkseid's Mother Box to activate a Boom Tube behind him, and Superman blasts Darkseid through with his heat vision. While Superman anticipates Darkseid's eventual return from Apokolips, Kara informs him that she changed the coordinates to a random spot in space, leaving Darkseid floating, helplessly frozen.

Having saved her cousin's life and found her place on Earth, Kara decides to use her powers to fight for altruism under the alias of Supergirl, and she is met with applause by Wonder Woman, the Amazons, and finally Batman. Superman and Supergirl fly to Metropolis together.